Conventionally, a display map in a car navigation device uses a color pallet for assigning display colors to constituent elements of the map display such as a road, a landmark and a name of a wide area. The color pallet is data for coloring so that the constituent elements correspond to displayed colors of the constituent elements.
For example, JP-A-3-7638 discloses a car navigation device which includes two kinds of color pallets, and switches between them depending upon the vehicle speed.
According to the above car navigation device, a large amount of map data is displayed for easily confirming the present position when the vehicle is traveling at a low speed, and important data only is displayed for maintaining safety when the vehicle is traveling at a high speed. Specifically, according to the above technology, small roads are displayed in the same color as the background color when traveling at high speeds, so that the small roads cannot be substantially seen by a user.
According to this technology, however, the data which cannot be substantially seen may, in practice, be what the user actually desires to confirm. Therefore, it is not desirable for the display data to be substantially erased even when the two color pallets are switched in displaying the map.